Real Dictionary

waterfall
countable noun: A waterfall is a place where water flows over the edge of a steep, high cliff in hills or mountains, and falls into a pool below.

waterfall in American English
a steep fall of water, as of a stream, from a height; cascade
noun: a steep fall or flow of water in a watercourse from a height, as over a precipice; cascade

waterfall in British English
noun: a cascade of falling water where there is a vertical or almost vertical step in a river